5.473 Logic must take care of itself.

A possible sign must be able to signify. Everything that is possible in logic is also allowed. (“Socrates is identical” therefore denominates nothing [heisst darum nichts] because there is no property that “identical” denominates. The proposition is nonsensical [unsinnig] because there is some arbitrary definition that we have not made, but not because the symbol in and of itself would be forbidden.)

We cannot, in a certain sense, go wrong in logic.

That is, there is a certain kind of error that one cannot make. Namely, the use of absolutely (not arbitrarily, or conventionally) forbidden symbols.

The first sentence of this remark is the same as the first sentence in the Notebooks 1914-1916. This is an important idea, apparently, for Wittgenstein.